Pedicle screw for intervertebral support elements

ABSTRACT

The pedicle screw ( 1 ) for intervertebral support elements ( 3 ) consists of a shaft ( 10 ) and a head ( 2 ) comprising at least two parts ( 20, 22 ). The head is formed as a securing means for at least one support element ( 3 ). Each support element consists of a piece of a cable-like band ( 31 ) and a cylindrical support body ( 30 ) with an axial lumen ( 31 ′) containing the band. The band is securable outside end surfaces ( 32 ) of the support body in the head. The head is formed with a contact surface ( 23 ) via which a pressure stress can be exerted on the support body in the band direction, and indeed using the band and in cooperation with a further pedicle screw. A part ( 20 ) of the head ( 2 ), which is firmly connected to the shaft ( 10 ) at the one end of the latter, contains a base groove ( 21 ) which is oriented transversally to the shaft and into which the part of the band ( 31 ) to be secured or a connecting piece ( 292 ) which contains the band can be introduced during the securing of the support element ( 3 ) by means of a translatory movement in the direction of the shaft and fixed there.

The invention relates to a pedicle screw for intervertebral supportelements in accordance with the preamble of claim 1.

Invasive treatment methods are known for the stabilization of spinalcolumns in which bone bridges are made to grow between adjacentvertebral bodies using implants. Stiffening fusions of the adjacentvertebrae result through the bone bridges. In addition to stiffeningoperations of this kind a treatment method for stabilizing by means ofan implant system is also known in which no fusion arises, but rather amobility is preserved between adjacent vertebrae. This implant systemcomprises pedicle screws and intervertebral support elements which areimplanted during the operation from the back. Each pedicle screw has ahead which is formed as a ring. In each case two pedicle screws arescrewed in a vertebral body through the pedicle passages of thevertebra. The support elements are secured at the screw heads. Twosupport elements which are arranged in parallel between adjacentvertebrae form a dynamic supporting of these vertebrae. Thevertebrae—with the exception of the lowermost lumbar vertebra—can ineach case also be connected at the same pedicle screws to an upwardlyand a downwardly adjacent vertebra through two pairs of supportelements. Each support element consists of a piece of a cable-like bandand a cylindrical support body which is elastically yielding. A rigidmaterial can also be used for individual support bodies in order tostiffen the spinal column at individual locations. The band is drawn inan axial lumen of the support body. The intervertebral support elementsare secured at the pedicle screws using the band. In this the bands mustbe drawn through the ring heads. The drawing in of the band is anoperation step which is difficult to carry out.

The object of the present invention is to create, for dynamic vertebrasupporting, a pedicle screw for intervertebral support elements forwhich the securing of the support element at the pedicle screw, whichmust take place during the surgical operation, can be carried out moreeasily. This object is satisfied by the pedicle screw which ischaracterized in claim 1.

The pedicle screw for intervertebral support elements consists of ashaft and a head which comprises at least two parts. The head is formedas a securing means for at least one support element. Each supportelement consists of a piece of a cable-like band and a cylindricalsupport body with an axial lumen which contains the band. The band canbe secured outside end surfaces of the support body in the head. Thehead is formed with a contact surface via which a pressure stress can beexerted on the support body in the band direction, and indeed using theband and in cooperation with a further pedicle screw. A part of thehead, which is firmly connected to the shaft at the one end of thelatter, contains a base groove which is oriented transversally to theshaft and into which the part of the band to be secured or a connectingpiece which contains the band can be introduced during the securing ofthe support element by means of a translatory movement in the directionof the shaft and fixed there.

Subordinate claims 2 to 11 relate to further advantageous embodiments ofthe pedicle screw in accordance with the invention.

The invention will be explained in the following in more detail withreference to the drawings. Shown are:

FIG. 1 a lumbar vertebra showing the position of two pedicle screws,

FIG. 2 two pedicle screws with an intervertebral support element for twoadjacent vertebrae,

FIG. 3 an outline illustration of adjacent lumbar vertebrae showing theposition of two implanted support elements,

FIG. 4 the head of a pedicle screw in accordance with the inventiontogether with a support element,

FIG. 5 a second embodiment of the head with a T-shaped groove-stone,

FIGS. 6, 7 two heads in which disc-shaped parts are arranged between thesupport element and the head,

FIG. 8 a head with a connector,

FIG. 9 a variant of the connector of FIG. 8,

FIG. 10 a head with a sleeve part

FIG. 11 a further embodiment of the head with a connector and

FIG. 12 a cross-section through the head of the embodiment in accordancewith FIG. 10.

A lumbar vertebra 9 in accordance with FIG. 1 consists of a vertebralhole 90, a vertebral body 91 and a vertebral arch 92 which comprises twopedicles 93, two transverse processes 94, a spine 95 of a vertebra andarticular processes 96. The positions of two pedicle screws 1 in theimplanted state are indicated in chain-dotted lines. In these positionsthe heads 2 of the pedicle screws 1 are located directly at the outerside of the pedicles 93 between the transverse processes 94 and thearticular processes 96. FIG. 2 shows two pedicle screws 1, which areprovided for two adjacent vertebrae 9 and between the heads 2 of which,which are formed as rings, an intervertebral support element 3 isarranged. Shafts 10 of the pedicle screws 1 are screwed in into thevertebrae 9. The heads 2 have notches 4 laterally which are required forthe implanting and orientation of the pedicle screws 1 by means of aninstrument. The support element 3 consists of a piece of a cable-likeband 31 and a cylindrical support body 30 in which the band 31 iscontained in an axial lumen 31′. The band 31 is secured outside of endsurfaces 32 of the support body 30 in each case in the heads 2 of thepedicle screws 1 with a setting screw 22. The heads 2 are provided withplanar contact surfaces 23 via which a pressure stress can be exerted onthe support body 30 in the band direction via their end surfaces 32,with the tension force required for this being produced using the band31 and in cooperation with the pedicle screw 1 of the adjacent vertebra9.

An outline drawing with two adjacent lumbar vertebrae 9 is shown in FIG.3. The positions of two implanted support elements 3 are indicated.

The pedicle screw 1 in accordance with the invention differs from theknown pedicle screw through a specially formed head 2. The supportelement 3 can be laid in into the latter by means of a translationalmovement in the direction of the shaft 2, so that the support element 3can be fixed in the head without a drawing in of the band 31 into aneye-like securing means being required.

A first embodiment of the head 2 of a pedicle screw 1 in accordance withthe invention is illustrated in FIG. 4 together with a support element3. A part 20 of the head 2 which comprises two lugs 20 a and 20 b andwhich is firmly connected to the shaft 10 contains a base groove 21which is oriented transversely to the shaft 10 and a thread 24. A partof the band 31 which is to be secured is inserted into the base groove21 during the securing of the support element 3 and is fixed with ascrew 22. The base groove 21 has a shape which corresponds to the shapeof the band in such a manner that the base groove is formedcomplementarily in the insertion region. An edge region 21′ of the basegroove 21 can—in order to prevent a damage to the inserted band 31—beformed in such a manner that the base groove 21 widens in the directiontowards the contact surface 23.

The embodiment of FIG. 4 is a first example of a pedicle screw inaccordance with the invention, in which the lugs 20 a, 20 b, which formflanks of the base groove 21, have depressions 24 on their inner sidesinto which a securing part, namely the screw 22, can be firmly anchoredby means of a form lock. After the production of the form lock the lugs20 a, 20 b are advantageously elastically spread apart somewhat by thesecuring part 22, so that the position of the latter is additionallyfixed as a result of an increased adhesive friction and thus of a forcelock.

A second example is shown in FIG. 5, in which the lugs 20 a, 20 b havegroove-like depressions 24 a on their inner sides. A T-shaped groovestone 25 with lateral ribs 25 a is pushed in between the grooves 24 aafter the insertion of the band 31—cf. FIG. 5—and for fixing the band 31a setting screw 22—cf. FIG. 5—is screwed into a bore in the groove-stone25 with inner thread 250.

FIGS. 6 and 7 show in each case a head 2 in which a disc-shaped part 26is arranged between the support element 3 and the head 2. The head 2 inFIG. 6 comprises a core part 20 and at least one disc-shaped part 26which forms the contact surface 23 to the cylindrical support body 30 ofthe support element 3 on the one side and which forms a contact surface261 to the core part 20 on the other side. The surface of the core part20 is made spherical. The contact surface 261 to the core part 20 of thedisc-shaped part 26 is made in the shape of a spherical sectioncorresponding to the shape of the core part 20. The disc-shaped part 26is applied together with the support body 30 to the band 31, with theband 31 being drawn into the bore 260. This drawing in of the band 31 iscarried out prior to the implanting of the support element 3 outside thebody of the patient to be operated on.

The head 2 in FIG. 7 comprises a core part 20 which has at each end ofthe groove 21 an elevation 262 which is formed to fit complementarily toa groove 263 of the disc-shaped part 26 (ridge-groove form lock). Thegroove 263 can be pushed onto the elevation 262 in the direction of theshaft 10. As was already the case in the example of FIG. 6, the part 26is applied to the band 31 prior to the implanting.

FIG. 8 shows a head 2 with a core part 20 and with a connector 27 whichis a sleeve-like part and the inner space of which has a square profilewhich is formed by planar surfaces. The core part 20 is tightly enclosedby the connector 27, so that a spreading open of the lugs 20 a, 20 bduring the screwing in of a screw 22 (see FIG. 10) into the thread 24 isprevented.

FIG. 9 shows a variant 27′ of the connector 27 of FIG. 8. This connector27′ is made longer in the direction of the groove 21 or of the bore 270and contains a bore with inner thread 272. The band 31 can additionallybe fixed below the threaded bore 272 with a second screw 22.

FIG. 10 shows a head 2 with a sleeve part 28 and with a core part 20which is firmly connected to the one end of the shaft 10. The screw-cappart 28 is displaceable along the entire shaft 10 up to the named shaftend. In this the thread 24 comes to lie over the groove 21 so that thescrew for the securing of the band 31 can be screwed into the thread 24.

FIG. 11 shows a further embodiment of the head 2 with a connector 29.The band 31 can be secured in the connector 29 in a bore 293. During theoperation the connector 29, which contains the band 31, is placed ontothe core part 20 of the head 2, with a connecting piece 292 of theconnector 29, which has a prismatic shape, being laid in into thecorresponding complementarily shaped groove 21. The securing between theconnector 29 and the core part 20 can be produced for example with twoscrews. The non-illustrated screws are inserted through bores 291 a ofthe connector 29 and are screwed tight in threaded bores 291 b of thecore part 20.

The embodiments in accordance with FIGS. 6 and 10 permit a so-called“polyaxiality” in the fixing of the support body 30 at the pediclescrews 1. The “polyaxiality” relates to the axis of the shaft 2; in allother body 30, which is given by the axis of their lumens 31′. The term“polyaxiality” is intended to mean that the angle between the two axisdirections is not fixed in advance, but can vary within a certainangular range. This will be explained for the embodiment in accordancewith FIG. 10 in more detail with reference to FIG. 12: FIG. 12 shows across-sectional illustration of the pedicle screw head 20 with thesleeve part 28, the inner surface 280 of which is a partial region of aspherical surface. The head 20 is made correspondingly spherical, sothat it can be laid in into the sleeve part 28 in different positions.The axis of the shaft 10 has a main direction z perpendicular to thedirection x of the support body 30 (x is perpendicular to the plane ofthe drawing). The shaft axis can deviate with respect to this maindirection z by an angle φ. This angle φ has a maximum value φ_(max)which amounts to 10° or even more, but which is less than 15°. The angleφ can vary in the region of a cone about the main direction z, with thehalf opening angle of this cone amounting to φ_(max). Correspondingremarks also hold for the embodiment in accordance with FIG. 6. Thesystem for the vertebral support which can be produced with the pediclescrews in accordance with FIGS. 6 and 10 is easier to implant thanks tothe “polyaxiality”.

Longitudinal components comprising support elements are anchored invertebrae with pedicle screws, with a dynamic stabilizing of thevertebrae being producible thanks to an elastic yielding of the supportelements. The pedicle screws in accordance with the invention permit ahead feeding of the longitudinal components. In the head feeding thelongitudinal components are laid in into the heads of the pedicle screwsin that merely a translational movement in the direction of the shaft inthat merely a translational movement in the direction of the shaft needbe carried out. Through a simple insertion of this kind the operationtechnique is obviously substantially simplified with respect to theolder treatment methods, in which the bands of the support elements mustbe drawn in into the screw heads, which are formed in ring shape.

1-11. (canceled)
 12. A dynamic supporting system for the spine, thesystem comprising: at least two pedicle screws, the pedicle screws eachhaving a shaft and a head, the head having an interior surface forming agenerally U-shaped channel extending from an open end of the head to abase of the head, the interior surface including a threaded portion; alongitudinal support element sized for insertion into the generallyU-shaped interior channel through translational movement of thelongitudinal support element in a direction generally parallel to theshaft, the support element having a non-rigid elastically yieldingsupport body positionable between the pedicle screws; at least one notchon an exterior surface of the head and configured for engagement with animplantation instrument; and at least two securing elements each sizedfor engagement in one of the threaded portions for connection of theelastically yielding support element between the pedicle screws.
 13. Thedynamic supporting system of claim 12, wherein the elastically yieldingsupport element further comprises: an elastic band contained partiallywithin an axial lumen of the support body.
 14. The dynamic supportingsystem of claim 13, wherein each securing element engages the elasticband.
 15. The dynamic supporting system of claim 13, further comprising:a groove at the base of the generally U-shaped channel for receipt ofthe band.
 16. The dynamic supporting system of claim 12, wherein thehead further comprises: a sleeve part; and a core part connected to oneend of the shaft, the core part being seated with the sleeve partallowing the shaft of the pedicle screw to move relative to the head.17. The dynamic supporting system of claim 12 further comprising: a pairof spaced lugs on the head and forming there between the U-shapedchannel.
 18. The dynamic supporting system of claim 12 wherein the headis coupled to the shaft for polyaxial relative movement.
 19. The dynamicsupporting system of claim 12 further comprising: at least one planarcontact surface on the head adapted to be juxtaposed against thelongitudinal support element.
 20. The dynamic supporting system of claim19 wherein the at least one planar contact surface is adjacent theU-shaped channel and spaced from the at least one notch.
 21. The dynamicsupporting system of claim 12 wherein the notch is elongate and axiallyoriented generally parallel with the pedicle screw shaft.
 22. Thedynamic supporting system of claim 12, wherein the elastically yieldingsupport element further comprises: an elastic band contained partiallywithin an axial lumen of the support body; wherein each securing elementengages the elastic band; and wherein the head is coupled to the shaftfor polyaxial relative movement.
 23. A dynamic supporting system for thespine, the system comprising: at least two pedicle screws, the pediclescrews each having a shaft and a head, the head having a pair of spacedlugs that form a generally U-shaped channel extending from an open headfeeding end of the head to a base of the head, the open head feeding endconfigured for insertion of a longitudinal component therein, aninterior surface of each lug including a threaded portion; a part forengaging the pedicle screw head; wherein the longitudinal component is asupport element having a non-rigid elastically yielding support bodypositionable between the pedicle screws, wherein the part is arrangedbetween the elastically yielding support body and the head; and at leasttwo securing elements each sized for engagement with one of the pediclescrew heads, the threaded portions and connection of the elasticallyyielding support element between the pedicle screws.
 24. The dynamicsupporting system of claim 23 wherein the head is coupled to the shaftfor polyaxial relative movement.
 25. The dynamic supporting system ofclaim 24 further comprising; an arrangement on an exterior surface ofthe head and configured for engagement with an implantation instrument.26. The dynamic supporting system of claim 25 wherein the arrangement isa notch.
 27. The dynamic supporting system of claim 26 furthercomprising a pair of the notches spaced diametrically on the head. 28.The dynamic supporting system of claim 25 wherein the arrangement iselongate and axially oriented generally parallel with the pedicle screwshaft.
 29. The dynamic supporting system of claim 27 further comprising:at least one planar contact surface on the head adapted to be juxtaposedagainst the longitudinal support element.
 30. The dynamic supportingsystem of claim 29 further comprising a pair of the planar contactsurfaces spaced diametrically on the head.
 31. The dynamic supportingsystem of claim 23, wherein the elastically yielding support elementfurther comprises: an elastic band contained partially within an axiallumen of the support body; wherein each securing element engages theelastic band; and wherein the head is coupled to the shaft for polyaxialrelative movement.
 32. A method for dynamic stabilization of the spine,the method comprising the steps of: inserting at least two pediclescrews into pedicles of adjacent levels of vertebra of the spine, thepedicle screws each having a head with a generally U-shaped channel; andinserting a supporting element into the generally U-shaped interiorchannel through translational movement of the supporting element in adirection generally parallel to the shaft, the support element having anelastically yielding support body positionable between the pediclescrews.
 33. The method of claim 32 further comprising: pre-arranging apart between the elastically yielding support body and the head of thepedicle screw.
 34. The method of claim 32 wherein the pedicle screwinserting step further comprises: engaging an implantation instrumentwith a notch on an exterior surface of the head of each pedicle screw;and rotating the implantation instrument and pedicle screw engagedtherewith.
 35. The method of claim 32 further comprising: juxtaposingthe supporting element against a planar contact surface on each of thepedicle screw heads.